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Endoscopic ultrasound highly accurate in evaluating ambiguous radiographic findings of the pancreas

August 28, 2008

Researchers from St. Louis University School of Medicine in Missouri report that EUS and EUS-FNA is 99.1 percent accurate in diagnosing pancreatic neoplasms (abnormal growths or tumors) in patients who were referred for endoscopic ultrasound (EUS) because of CT and/or MRI reports of two common, though somewhat ambiguous findings - enlargement of head of pancreas (HOP) or dilation of the pancreatic duct (PD). The study appears in the August issue of GIE: Gastrointestinal Endoscopy, the monthly peer-reviewed scientific journal of the American Society for Gastrointestinal Endoscopy (ASGE).

Occasionally, patients who are asymptomatic or who have nonspecific symptoms, such as weight loss and abdominal pain, have subtle abnormal or incidental findings on CT and/or MRI that raise suspicion for pancreatic cancer. These tests have relatively low specificity (ability to definitively discern between various diagnoses) in this setting. Perhaps due to a concern of missing early, small pancreatic cancers, physicians who perform EUS are increasingly referred patients with subtle CT or MRI findings such as ''enlarged pancreatic head" or ''dilation of the pancreatic duct (widening of the main duct coursing through the pancreas)." Endoscopic ultrasound and endoscopic ultrasound-guided fine needle aspiration (EUS-FNA) have become a valuable tool in the diagnostic evaluation of patients with suspected pancreatic cancer. This technique allows for detection and possible needle biopsy of small pancreatic tumors even before they can be visualized as a discrete mass with CT or MRI. According to the American Cancer Society, deaths from pancreatic cancer in 2008 are estimated to be approximately 34,000.

"Often, patients with these radiologic findings are referred for EUS in lieu of waiting for repeated imaging. Our study looked to determine the performance characteristics of EUS and/or EUS with FNA in diagnosing a pancreatic tumor in this patient population," said study lead author Banke Agarwal, MD, Saint Louis University School of Medicine. "We found that EUS and/or an EUS-FNA for diagnosing a pancreatic neoplasm was 99.1 percent accurate with 88.8 percent sensitivity and 100 percent specificity."

Endoscopic ultrasound consists of a flexible endoscope which has a small ultrasound device built into the end. The ultrasound component produces sound waves that create visual images of the digestive tract which extend beyond the inner surface lining. EUS can be used to evaluate an abnormality below the surface such as a growth that was detected at a prior endoscopy or by X-ray. EUS can also be used to diagnose diseases of the pancreas, bile duct, and gallbladder when other tests are inconclusive, and can be used to determine the stage of cancers. Tissue samples, using a fine needle aspiration technique (FNA), can be obtained in real time with EUS guidance should an abnormality be seen.

Patients and Methods

This study was a retrospective analysis of 110 patients, mean age 60.3 years, from a prospectively maintained database of patients who underwent an EUS and/or EUS-FNA at St. Louis University Hospital between March 2002 and March 2006 for suspected pancreatic cancer based on an abnormal CT and/or MRI who were reported as having an enlarged HOP or dilation of the PD (with or without a dilated common bile duct). An EUS examination was initially performed by using a radial echoendoscope. Whenever a suspicious "mass" was identified on radial EUS, an FNA was performed using a linear echoendoscope. Fine needle aspirates were submitted for cytology and biochemical analysis. A final diagnosis was based on definitive cytology, surgical pathology or clinical follow up of 12 months or more (median follow up was 16 months).

Results

Researchers found that 6 percent of patients referred because of an enlarged HOP on a CT and/or an MRI and 11.5 percent of patients referred for a dilated PD had a pancreatic neoplasm. The diagnostic accuracy of an EUS and/or EUS-FNA in these patients for diagnosing a pancreatic neoplasm was 99.1 percent. Furthermore, no patient with enlarged HOP, but without a mass at EUS, went on to develop cancer.

In conclusion, researchers found that a pancreatic neoplasm is present in a clinically significant number of patients with an ''enlarged HOP'' or "dilated PD" detected on a CT and/or MRI performed for evaluation of nonspecific symptoms, such as abdominal pain or weight loss. They also observed that an EUS and/or EUS-FNA are highly accurate for the diagnosis of pancreatic neoplasm in these patients. Based on these data, researchers recommend that an EUS and/or EUS-FNA be considered as the logical next test in the evaluation of patients with such imaging findings.

American Society for Gastrointestinal Endoscopy